1. Field of the Invention
The present invention relates to a technique for removing particles from substrate surfaces or liquids in a substrate processing apparatus for processing substrates, such as semiconductor substrates and glass substrates for liquid crystal displays or for photomasks, using liquids.
2. Description of the Background Art
In the substrate manufacturing process, there are conventionally known substrate processing apparatuses for performing predetermined processing on substrates by supplying liquids such as pure water and chemical solutions to the substrates. There are mainly two types of such substrate processing apparatuses: batch substrate processing apparatuses for processing a plurality of substrates at a time which are immersed together in a liquid retained in a processing bath; and single-substrate processing apparatuses for processing a single substrate held by a holder one by one by discharging a liquid onto the substrate surface.
Those substrate processing apparatuses remove particles attached on substrates or floating in liquids as appropriate. Particles are usually removed by forming liquid flows along substrate surfaces and carrying particles by the action of the liquid flows. In some cases, particles are removed by supplying bubbles in liquids to adsorb particles on the bubbles and carry them together.
However, there is a certain limit on the efficiency of particle removal by only using the action of liquid flows. Further, even in the case of using bubbles, bubble sizes usually generated with a bubbler are overwhelmingly larger than particle sizes and thus not optimum for particle removal. In recent years, the level of particles allowed in substrate processing is becoming higher. Accordingly, more efficient techniques for particle removal are required.